1. Field of the Invention
The present invention relates to a technology for thickening an image to be printed.
2. Description of the Related Art
With an increase in a print resolution, a printing apparatus can perform printing more finely. Therefore, reproducibility of lines or characters of images become more important. However, the reproducibility of lines or characters may be changed due to a use environment or long-term use of a printing apparatus, and thus the lines or characters may be printed more thinly than the original thickness thereof in some cases. When the lines or characters become thin, the impression of a print product is considerably changed. Therefore, it is important to maintain the reproducibility of the lines or characters. Japanese Patent Application Laid-Open No. 10-313410 discusses an image processing method for thickening lines or characters on a print product by performing correction so that pixels adjacent to a black pixel, which is a target pixel, are substituted with black pixels to thicken an image before printing. In the method discussed in Japanese Patent Application Laid-Open No. 10-313410, however, a correction amount may be different depending on the angle of an element included in a line or character in the image. Specifically, as in FIGS. 15A and 15B, elements of graphics “\” and “|” are corrected, and thus correction amounts in the right and left directions of the graphics are seen. In this case, the correction amount (thickening amount) for the element of “|” is for one pixel substituted with a black pixel, but the correction amount for the element of “\,” is for two pixels substituted with two black pixels. Thus, the amounts for thickening an image are different from each other.